1. Field of the Invention
The present invention relates to a liquid crystal display device and a method for manufacturing the same, and more particularly to a liquid crystal display device in which the structure of an array substrate and a liquid crystal dripping area are improved and a method for manufacturing the same.
2. Description of the Prior Art
In a conventional method for manufacturing liquid crystal display panels, liquid crystal is interposed between an array substrate and a color filter substrate (hereinafter, referred to as a CF substrate), both of the substrates are stuck together to make a panel, and then the panel is cut and separated into individual display panels. As a method for interposing liquid crystal between both substrates at this case, there are a method of injecting and filling liquid crystal into a panel area to become a display portion of an array substrate and a method of dripping and filling the liquid crystal into such a panel area. Japanese Patent Laid-Open Publication No. Hei 5-119,325 has disclosed a method of filling liquid crystal using double seals of an outer seal and an inner seal by a liquid crystal injection method. In case of using such a liquid crystal injection method, however, a liquid crystal injection inlet for having liquid crystal injected through it must be provided in a seal and this injection inlet comes to hinder the vacuum at the time of sticking the substrates together.
Therefore, in a recent production process of liquid crystal display devices, a liquid crystal filling method by means of a liquid crystal dripping method is used in general.
A liquid crystal filling method by a liquid crystal dripping method is described in the following.
FIG. 1 is a plan view of an array substrate to be used in a conventional liquid crystal display device. As shown in FIG. 1, an array substrate 1A to be used in a conventional liquid crystal display device comprises first seal frames 2 for forming panel areas 4 to become panel display portions by having liquid crystal dripped on them. A large single second seal frame 3A is provided outside the first seal frames 2 so as to contain four first seal frames 2 inside it. Each of these seal frames 2, 3A functions as an adhesive agent for sticking the array substrate and a color filter substrate (not shown) on each other. The inner area of a first seal frame 2 is an area to have liquid crystal dripped on it. The second seal frame 3A is provided in an outer area of the display portions of the array substrate 1A. The four corners of the second seal frame 3A are cut out in order to smooth the flow of air at the time of breaking a vacuum.
A seal inner passage is formed between the first seal frames 2 of the array substrate 1A. A seal outer peripheral passage 6 is formed between the first seal frames 2 and the second seal frame 3A. Detailed description of a CF substrate is omitted.
FIG. 2 is a figure for explaining an example of the production flow of a conventional liquid crystal display device. As shown in FIG. 2, the upper left half of the figure is the production flow of an array substrate 1A and the upper right half of it is the production flow of a CF substrate.
First, both of an array substrate and a CF substrate are washed and dried. Then, an oriented film (orientation material) is applied or printed onto the surface of each of the substrates. And both the substrates are dried to evaporate a solvent contained in the orientation material. After this, rubbing is performed on both the substrates to give an orientation to the applied orientation material. Subsequently, both the substrates are washed and dried.
Next, a seal material is applied to the array substrate and a patterning process is performed on it. In this patterning process, first seal frames 2 for sealing the periphery of a panel display portion in the shape of a closed loop is first formed. Further, a second seal frame 3A having its four corners cut out is formed so as to contain the first seal frames 2. As a method of forming these seals, a drawing method using a seal dispenser device is used. On the other hand, a spacer material is scattered on the CF substrate.
The liquid crystal injection method and the liquid crystal dripping method are the same as each other with regard to the procedure up to here.
Next, a necessary amount of liquid crystal is dripped on the inside (display panel portion) of a first seal frame 2 on the array substrate. This dripping of liquid crystal is performed using a dispenser device dedicated to liquid crystal. In short, the amount of liquid crystal necessary for a display surface is calculated in advance and the calculated amount of liquid crystal is dripped on the inside, namely, the display surface of the first seal frame 2. And the spacer scattered on the CF substrate is fast stuck on the CF substrate by being raised in temperature in an electric furnace.
When the dripping of liquid crystal and the sticking of spacer have been finished, both the substrates are transferred into a vacuum chamber. This vacuum chamber is evacuated so as to be depressurized to about 10−2 Pa inside it. Both these substrates are stuck on each other with the first seal frames 2 and the second seal frame 3A between them in a vacuum atmosphere. The seals are hardened in a temporarily hardened state at this time.
Next, the vacuum chamber is released (broken in vacuum) and both the substrates stuck together are taken out from the chamber. Then, both the substrates stuck together are raised in temperature in an electric furnace to properly harden the seal frames 2 and 3A being in a temporarily hardened state.
Further, both the substrates being in a single sheet state are cut out into individual panels. The panels obtained by cutting are washed and then such a panel post-process as a polarizing-plate sticking process and the like is performed on the panels. The above-mentioned procedure is the production flow of a liquid crystal display device.
Next, concrete steps of production are described with reference to FIG. 3A to FIG. 3E.
First, as shown in FIG. 3A, with regard to this liquid crystal display panel, first seal frames 2 and a second seal frame 3A are formed on an array substrate 1A. Liquid crystal 7 is dripped and filled in the inside of the first seal frames 2 before a CF substrate 8 is stuck on the array substrate 1A. Space 9 is formed in seal inner passage 5 and seal outer peripheral passage 6 (see FIG. 1 for both the passages).
Next, as shown in FIG. 3B, the CF substrate 8 is placed over the array substrate 1A. As a result, a large space 9 is formed in the inner passage and a small space 9 is formed in the outer peripheral passage.
Further, as shown in FIG. 3C, both the substrates are stuck together in a vacuum chamber being evacuated. At this time, both the substrates are supported by the two sealing means of the first seal frames 2 and the second seal frame 3A at the seal outer peripheral passage side. And both the substrates are supported by single means of only the first seal frames 2 at the seal inner passage side. The space 9 formed at the seal inner passage side is liable to be more influenced by the vacuum pressure since it is wider. Due to this, both the substrates come to receive respectively pressures in the arrow directions from the outside.
Next, as shown in FIG. 3D, when after properly hardening the seals both the substrates are taken out from the chamber and cut into individual panels, the panels being in a state where the space 9 at the seal inner passage side is collapsed result in being obtained (before washing).
Further, as shown in FIG. 3E, the array substrate 1A and the CF substrate are not made parallel with each other even when the panels are washed, and the panels are sent to a subsequent process as being kept in a state where the inner passage side is lower in particular. So-called defective products occur (after washing).
In short, since nothing is sealed between patterns of the first seal and the second seal, a vacuum state occurs and the action of the first seal as a fulcrum results in producing a state of uneven gap around a panel.